In 3rd Generation Partnership Project (3GPP), studies have been carried out on LTE-Advanced (hereinafter, abbreviated as “LTE-A”). In LTE-A, the introduction of a bandwidth expansion technology called “carrier aggregation (CA)” has been studied. In LTE-A carrier aggregation, an approach is taken in downlink (DL) and uplink (UL) channels that achieves high speed transmission by aggregating a plurality of carriers, i.e., by bundling component carriers (CCs) each having 20 MHz, for example. In LTE-A, studies have been carried out on bandwidth expansion through the introduction of five CCs, i.e., up to 100 MHz, as a possible range.
In this respect, studies have been carried out at the same time on a transmission power control method targeting UL CA. In the studies on UL transmission power control in LTE-A, the following matters (A) to (C) have been agreed. CC-specific transmission power control is performed (A). CC-specific (for each UL channel) maximum transmission power Pcmax, c, and UE (User Equipment) specific (UE-specific) maximum transmission power Pcmax (upper limit of total maximum transmission power on a plurality of CCs) are provided (B). In addition, when the transmission power of each UL channel transmitted on one CC exceeds the CC-specific (for each UL channel) maximum transmission power, or when the total value of transmission power of UL channels transmitted on a plurality (all) of CCs in simultaneous transmission of a plurality of UL channels exceeds a UE-specific maximum transmission power, control called power scaling, which reduces the transmission power of a UL channel, is performed (B). In UL CA, the power allocation priority rule for a plurality of UL channels when power scaling occurs in simultaneous transmission of a plurality of UL channels is agreed as follows (C).PUCCH>PUSCH with UCI>PUSCH without UCI
PUCCH stands for Physical Uplink Control CHannel, and PUSCH stands for Physical Uplink Shared CHannel. UCI is an abbreviation for Uplink Control Information, and for example, includes the following control information, specifically. UCI includes acknowledgment/non acknowledgment (ACK/NACK), rank indicator (RI), channel quality information (CQI), pre-coding matrix indicator (PMI) and channel state information (CSI). A periodic or aperiodic transmission method is used for transmitting the information such as CSI and CQI, for example.
In addition, the term “PUSCH with UCI” refers to a PUSCH on which UCI is multiplexed, and the term “PUSCH without UCI” refers to a PUSCH on which no UCI is multiplexed. Accordingly, when power scaling occurs in simultaneous transmission of a plurality of UL channels, the transmission power is allocated in the following order: the transmission power for PUCCH; the transmission power for PUSCH on which UCI is multiplexed; and the transmission power for PUSCH on which no UCI is multiplexed. This rule applies regardless of whether these channels are on the same CC or on different CCs.
Meanwhile, studies have been carried out on a power allocation rule used when power scaling relating to a periodic sounding reference symbol (SRS) or an aperiodic SRS used for measuring a channel quality such as CQI occurs. The power allocation rule can be classified into the following three cases (A) to (C), for example.
(A) Priority between a (periodic/aperiodic) SRS and a different UL channel (such as PUCCH or PUSCH) is as follows. Specifically, Non-Patent Literature (hereinafter, abbreviated as “NPL”) 1 describes the following priority used when power scaling occurs.PUCCH>SRS>PUSCH
Accordingly, when power scaling occurs, the transmission power for a terminal is preferentially allocated in the order of a PUCCH, an SRS, and a PUSCH.
(B) Priority between a periodic SRS and an aperiodic SRS is as follows. Specifically, NPL 2 describes the following priority used when power scaling occurs.Aperiodic SRS>Periodic SRS
Accordingly, when power scaling occurs in simultaneous transmission of a periodic SRS and an aperiodic SRS, the transmission power is preferentially allocated in the order of an aperiodic SRS, and a periodic SRS.
(C) Priority between a plurality (periodic or aperiodic) of SRSes is as follows.
NPL 1 describes a power allocation priority rule used when a plurality of periodic SRSes are simultaneously transmitted on a plurality of CCs. Specifically, NPL 1 discloses a method of determining priority for transmission power for periodic SRSes in accordance with UL CC ID numbers as illustrated in FIG. 1. FIG. 1 is a conceptual diagram for allocating larger transmission power in descending order of ID numbers of UL CCs when power scaling occurs in simultaneous transmission of periodic SRSes on three CCs. Accordingly, each terminal can appropriately determine the transmission power of a periodic SRS for each of the CCs in accordance with this rule even when power scaling occurs in simultaneous transmission of periodic SRSes on a plurality of CCs.